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Darwinian Revolutions

ALLEN MACNEILL: On September 17, 1835, the Beagle moved into St. Stephen's Harbor. The bay swarmed with animals. Fish, sharks, and turtles were popping their heads up in all parts. The black lava rocks on the beach are frequented by large, most disgusting clumsy lizards. They are as black as the porous rocks over which they crawl and seek their prey from the sea. Somebody calls them imps of darkness. That's how Charles Darwin, English naturalist, author of The Origin of Species, and co-founder of the theory of evolution by natural selection, described the marine iguanas of Hood Island in the Galapagos archipelago.
I'm Allen MacNeill. I teach biology and evolution at Cornell University. And I'm here at this wonderful place, the Museum of the Earth at the Paleontological Research Institution in Ithaca, New York, as your host for this cyber tower series on the Darwinian revolutions. In 2009, we celebrate three significant events in the history of evolution and evolutionary theory. On February 12, 2009, we celebrate the 200th anniversary of the birth of Charles Darwin, author of The Origin of Species, The Descent of Man, and the founder of the discipline of evolutionary biology. In 2009, we also celebrate the 200th anniversary of the publication of Jean-Baptiste Lamarck's most famous book, Philosophie Biologique, in which he presented his own theory of evolution. And in November 2009, we celebrate the 150th anniversary of the publication of Charles Darwin's Origin of Species.
Theodosius Dobzhansky, one of the founders of the modern evolutionary synthesis, said nothing in biology makes sense, except in the light of evolution. In The Origin of Species, Darwin actually presented two theories-- one, which he called descent with modification, is the theory we now think of as evolution, the idea that species have changed over time from some remote ancestor in the distant past. The other theory is the theory of natural selection, which Darwin used to explain the origin of what we call evolutionary adaptations.
In this series, we will see some of the evidence that Darwin used to support his theory of evolution. And we will see how that evidence was used by scientists who eventually accepted both his theory of evolution and the mechanism that he proposed for it-- natural selection. This acceptance has not come easily. Although most scientists accepted Darwin's theory within about 10 years of its publication in 1859, the part of it they accepted was the idea of descent with modification. His theory of natural selection, however, did not fare as well.
By 1900, in fact, the theory had fallen almost entirely out of favor. At the same time that Darwin published his famous book, an Austrian monk named Gregor Mendel was working on a new theory to explain the inheritance of the characteristics of living organisms. The rediscovery of Mendel's theory of particulate inheritance not only formed the foundation of the new science of genetics, it also provided what many scientists viewed as a different mechanism for the origin of species.
Rather than Darwin's natural selection, these early geneticists believed that macro mutations, or large scale heritable changes, in the characteristics of organisms were the engine that produced new species. However, during the first half of the 20th century, Darwin's theory was resurrected in a collaborative effort of many scientists over about 20 years, an effort which eventually came to be called the modern evolutionary synthesis. As part of this effort, they integrated Mendel's theory of genetics with theories of population genetics, paleontology, botany, and ecology into that integrated theory we now think of as the evolutionary biology of the 20th, and now 21st, centuries.
Central to the development of the modern synthesis was the recognition that the key to understanding evolution is understanding the engines of variation-- that is, how the many differences between individual organisms are produced and inherited. The modern evolutionary synthesis was a landmark in the history of the theory of evolution. Widely celebrated in 1959 at the centennial of the publication of The Origin of Species, it was as significant to the science of evolutionary biology as quantum mechanics was to physics, and just as revolutionary.

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Published 150 years ago, Charles Darwin's On the Origin of Species provided the foundation for the modern science of biology. It also set in motion a revolution in the sciences and in our understanding of ourselves and our place in nature.

This CyberTower Study Room is a brief introduction to Darwin's theory and its implications. Beginning with an overview of Darwin's predecessors, we learn how Jean Baptiste Lamarck set the stage for Darwin's monumental achievement with his Philosophie Zoologique, which advanced a theory of evolution by means of the inheritance of acquired characteristics.

Darwin, whose academic training at Cambridge University was in Anglican theology, became an acclaimed naturalist and science writer following the five-year voyage of HMS Beagle. Using the notes and specimens that he had collected during the voyage, Darwin spent twenty years refining his theory, first published in 1859, of evolution by natural selection.

In the last segment of this Study Room, we visit the Museum of the Earth in Ithaca, New York, whose director, Dr. Warren Allman, discusses the importance of such museums to the science of evolutionary biology. We also hear from Cornell professor William Provine, who discusses Darwin's work and its importance to the history and philosophy of biology.